A Free Educational Resource Created by Carnegie Mellon University to Empower You to Secure Your Part of Cyberspace

Port Scanning

Trying to find open ports on a computer in order to gain access to it

Your computer has numerous ports, which are like doors to your computer. Some ports are used to plug in physical devices, such as your mouse, keyboard, printer, monitor, etc. Others are virtual ports that allow information to flow between your computer and a network. By blocking or opening these virtual ports, you can control what kinds of data can flow through your network

Port scanning is when an attacker tries to find open ports on your computer. By using certain tools, a hacker can send data to each port sequentially. Based on the response he gets, he can tell which ports are open. The hacker can then try to use these open ports to gain access to your computer.

There are a number of port scanning and port scan detection software tools available on the market, and you can do port scans on your own computer to check that your network is secure. If you would like to try this on your work computer, make sure you first get approval from your system administrator.

Protective Measures

Tools

  • Port scanner: Using a port scanner, you can scan your own ports and find out what an attacker would see if he were to port-scan your network. Once you find out which ports are open, you can decide if these ports need to be accessible from outside your network. If they do not, you should shut them down or block them using a software tool designed for network security.

    Nmap ("Network Mapper") is a free open-source tool that can be used for port scanning. It was designed to rapidly scan large networks, but it also works well for single computers. Nmap runs on most types of computers, and both console and graphical versions are available. You can download Nmap at http://www.insecure.org/nmap/ .

References

Links

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